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In this study, the effect of different heat treatment processes applied to AA7075 alloys on the fatigue behavior was examined. The processes applied to AA7075 aluminum included annealing (O), high temperature pre-precipitating (HTPP), artificial aging (T6), retrogression and re-aging (RRA). The annealing heat treatment was performed for 2 hours at 500°C and samples were cooled in the furnace. In the artificial aging (T6) process, after the samples were solution treated for 2 hours at 500°C, they were quenched at room temperature and aged for 24 hours at 120°C. In the retrogression and re-aging process, samples were solution treated for 1 hour at 220°C after the T6 process and then re-aged for 24 hours at 120°C. In the high temperature pre-precipitating, pre-precipitates were formed for 30 minutes at 450°C and then, it was aged for 24 hours at 120°C. All samples were characterized through the scanning electron microscope (SEM + EDS), hardness measurements and X-ray difraction (XRD) techniques. At the end of experimental studies, SEM and EDS examinations XRD results revealed that η (MgZn 2 ) phase formed in the microstructure following the HTTP, RRA and T6 heat treatment processes. As a result of the fatigue tests, the highest fatigue strength was measured in samples treated with artificial aging (T6), the lowest fatigue strength was measured in the annealed (O) samples.

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This study aims to determine optimum sintering and heat treatment parameters of powder injection moulded Nimonic-90 powder parts. Determination of optimum heat treatment conditions for sintered parts aimed to achieve maximum densities, and the microstructure and mechanical properties of the produced parts were characterised in sintered and heat treated conditions. Injection moulding feedstock was prepared by mixing Nimonic-90 powder with a multicomponent binder system. After moulding, the samples were subjected to a debinding process that consists of solvent and thermal steps. To determine the sintering temperatures, the debinded samples were subjected to differential scanning calorimetry analysis, and then they were sintered at various temperatures under high level vacuum. After sintering, density measurements and optical microscope examinations were performed. The highest density values were determined for the samples that were sintered at 1330uC for 3 h. Different aging treatments were performed on the samples that achieved the highest sintered density, and the microstructures and mechanical properties were then characterised. It was determined that heat treatments had a beneficial effect on the mechanical properties of the material. Though the mechanical properties of the injection moulded materials produced were lower than the wrought Nimonic-90 materials, they have superior mechanical properties compared with cast Nimonic-90 alloys.